The present disclosure relates, in various embodiments, to thin-film transistors (TFTs) and/or other electronic devices comprising a gate dielectric layer. The gate dielectric layer is formed from a dielectric composition as described herein that contains an infrared (IR) absorber or IR absorbing agent. This allows the dielectric composition to be selectively cured while its substrate remains at a relatively lower temperature, preventing deformation of the substrate.
TFTs are generally composed of, on a substrate, an electrically conductive gate electrode, source and drain electrodes, an electrically insulating gate dielectric layer which separate the gate electrode from the source and drain electrodes, and a semiconducting layer which is in contact with the gate dielectric layer and bridges the source and drain electrodes. Their performance can be determined by the field effect mobility and the current on/off ratio of the overall transistor. High mobility and high on/off ratio are desired.
There is interest in organic thin-film transistors (OTFTs) for applications such as radio frequency identification (RFID) tags and backplane switching circuits for displays, such as signage, readers, and liquid crystal displays, where high switching speeds and/or high density are not essential. OTFTs may be made using low-cost solution or liquid fabrication techniques. They also have attractive mechanical properties such as being physically compact, lightweight, and flexible.
Recently, there has been an increased interest in organic thin-film transistors which can potentially be fabricated using solution-based patterning and deposition techniques, such as spin coating, solution casting, dip coating, stencil/screen printing, flexography, gravure, offset printing, ink jet-printing, micro-contact printing, and the like, or a combination of these processes. Such processes are generally simpler and more cost effective compared to the complex photolithographic processes used in fabricating silicon-based thin-film transistor circuits for electronic devices. To enable the use of these solution-based processes in fabricating thin-film transistor circuits, solution processable materials are therefore required.
In this regard, gate dielectric layers may be formed by these solution-based processes. However, the gate dielectric layer so formed should be free of pinholes and possess low surface roughness (or high surface smoothness), low leakage current, a high dielectric constant, a high breakdown voltage, adhere well to the gate electrode, be stable in solution at room temperature, and offer other functionality. It should also be compatible with semiconductor materials because the interface between the dielectric layer and the organic semiconductor layer critically affects the performance of the TFT.
Roll-to-roll manufacturing refers to the process, still somewhat in development, of creating electronic devices on a roll of flexible plastic or metal foil, similar to the gravure, offset, and flexographic printing processes used with paper. It is contemplated that large circuits made with thin-film transistors and other devices can be easily patterned onto these large substrates, which can be up to a few metres wide and 50 km long. This type of manufacturing would allow for large-scale low-cost devices, especially when compared to normal semiconductor manufacturing processes that use photolithography techniques.
Low temperatures and increased speed of processing are critical to roll-to-roll manufacturing. In this regard, a solution processable dielectric layer is generally applied as a solution and then cured. The thermal curing generally occurs at a temperature, for example, from about 140° C. to 180° C. and for a period, for example, from 10 minutes to 30 minutes, to ensure optimal performance of the resulting composition. These curing temperatures and times are, in most cases, not compatible with roll-to-roll manufacturing.
It would be desirable to provide a dielectric layer and/or dielectric composition that could be processed at lower temperatures and/or shorter time periods, to allow for manufacture of an electronic device using roll-to-roll manufacturing and other processes.